The organizing Goal of Project 2 is to understand how the physicochemical composition and structure of engineered nanoparticles (ENPs) dictate ENP biokinetics and biological response in mice. This research will be conducted using custom-designed materials that contain a super paramagnetic iron oxide core, fluorescent labels, and functionalized to provide a range of net charges. In Aim 1 we will characterize the biokinetics of functionalized iron, cerium, and silica oxides following inhalation exposure using a novel Magnetic Particle Detection system and fluorescence microscopy for quantitation and localization of the ENPs. The biokinetic results will be formalized in a Physiologically-Based Pharmacokinetic model. In Aim 2 we hypothesize that genetic defects in the reficuloendothelial system, (loss of scavenger receptors) will modify the tissue/cellular biokinetics of ENPs according to their size and net charge. We also propose that the tissue/cell dose and biokinetics of ENPs in mice will be perturbed by perturbation of pulmonary function via structural changes in the lower respiratory tract. The consequences of these genotype and phenotype modifications on nanoparticle biokinefics should be reflected by changes in the inflammatory response. Aim 3 will relate these biokinetic and biochemical results to altered susceptibility to pulmonary infection by Streptococcus pneumoniae. The results from Project #2 will provide the critical experimental link between the in vitro mechanistic focus of Project #1 and the risk assessment focus of Project #3. This link is facilitated by use of highly parallel experimental systems, test materials, biological response assays, and statistical approaches to rank response across levels of biological organization. This Project is innovative for its focus on susceptibility and clinically important endpoints.